JPH11161129A - Method for detecting transferred image aberration and method for correcting aberration for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detecting method of the transferred image aberration of an image forming device which detects a deviation value without arranging the various kinds of sensors for measuring the deviation value at the inside of an image forming device main body. SOLUTION: As for the detecting method of the transferred image aberration by the transferred state of a test pattern printed on a recording medium, the test pattern is formed of a set of first patterns(25a, 26a, 27a and 28a) formed in a striped state by having a specified line width and a specified interval and second patterns(25b, 26b, 27b and 28b) having an interval different from that of the first pattern which are mutually opposed, and the set is printed on the left end part and the right end part of the recording medium in a carrying direction, so that the deviation value is detected from the value of the coincident part of the first pattern and the second pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having an apparatus for correcting a positional deviation of an image transferred to a recording medium, and to correct the positional deviation based on a transfer condition of a test pattern printed on the recording medium. The present invention relates to a method for detecting a position shift of a transferred image of an image forming apparatus and a method for correcting the position shift.

[0002]

2. Description of the Related Art Generally, an image forming apparatus for a color image, when transferring an image formed on the surface of a photoreceptor to a recording medium, individually and simultaneously prints a plurality of primary color dots on the recording medium. It is necessary to transfer the light beam to a position, and two separate light beams are emitted from the two light sources emitted from the light deflector, respectively. Separate reflectors are provided, each having an optical device for deflecting and entering a separate photoconductor.

In the above-described image forming apparatus, when light beams incident on at least two photosensitive members are transferred onto a recording medium, the trajectories of the light beams on the two photosensitive members due to a manufacturing error of each member. Light beams are incident on the respective photoconductors so that are transferred to the recording medium while being shifted from each other.

As shown in FIG. 6 (1), these deviations include a top margin deviation that shifts in the front and rear directions of the recording paper,
(2) a left margin shift in which the optical scanning start position shifts left and right, (3) a tilt shift in which both trajectories of the light beam intersect each other, or an extension line of both trajectories intersects each other;
It is inevitable that magnification gosa or the like in which the lengths of both trajectories of the light beam do not match as in (4) will occur.

Therefore, as described in Japanese Patent Application Laid-Open No. 3-142412, the left margin deviation can be eliminated by appropriately adjusting the scanning timing, and the top margin deviation, the inclined gosa and the magnification gosa are located downstream of the optical deflector. A technique for adjusting the position of a reflector provided on the side is known.

In the reflector adjusting means of the prior art, a total of three actuators are arranged at both ends of the reflector extending in the longitudinal direction and at an intermediate portion thereof, and the magnification gosa is controlled by the actuator at the intermediate portion. The top margin shift is adjusted by driving both of the actuators at both ends at the same time, and the tilt shift is adjusted by driving one or both of the actuators.

However, the prior art uses three actuators, which complicates the configuration and increases the cost. In addition, the prior art has a choice in determining how to operate the three actuators. In many cases, the operation becomes complicated.

Further, each of the optical gosa shown in FIG. 6 often appears as a composite of two or more than each optical gosa alone. Therefore, a mechanism for eliminating a plurality of composite gosa by a single operation is desired. It is rare.

Under such circumstances, the applicant of the present invention has disclosed at least one of optical deviations of the irradiation beam on the photosensitive drum,
Alternatively, a separate application has been filed for an image forming apparatus capable of eliminating a composite gosa with a single operation.

[0010]

However, in order to know the optical shift amount of the transferred image, which is the premise, the shift amount must be measured. For this purpose, a method of arranging various sensors in the image forming apparatus main body is known. However, the adjustment of the deviation amount is performed at the time of manufacture of a product, installation at a user's place of use, replacement of a photosensitive drum, and the like. In such a situation, providing a high-precision sensor and its processing circuit to the apparatus main body unnecessarily increases the cost.

In view of the above circumstances, the present invention provides a method for detecting a displacement of a transferred image in an image forming apparatus, which detects the amount of displacement without disposing various sensors for measuring the amount of displacement in the main body of the image forming apparatus. With the goal. It is another object of the present invention to provide a method for correcting a transfer image position shift of an image forming apparatus, which corrects the shift amount.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems. Claims 1 to 4 of the present invention relate to the first invention, and are directed to a test pattern printed on a recording medium. The present invention relates to a method for detecting a displacement of a transferred image of an image forming apparatus, which detects a displacement of an image transferred to a recording medium depending on a degree of transfer. The present invention relates to a method for detecting a displacement.

According to a first aspect of the present invention, a test pattern printed on a recording medium includes a first pattern formed in a stripe pattern at a constant line width and a constant interval, and a second pattern having a different interval from the first pattern. Are formed in a pair of pairs facing each other,
The pair of pairs is printed on the left end and the right end in the conveyance direction of the recording medium, and the amount of deviation is detected from the value of the matching portion between the first pattern and the second pattern.

Here, the "shift amount between the left end and the right end" means a combination of the shift amount at the left end and the shift amount at the right end. Therefore, it means the deviation amount of the left end or the right end, the combination of the deviation amount of the left end and the right end, or the difference of the deviation amount of the left end and the right end.

As described above, according to the first aspect of the present invention, the deviation from the value of the coincidence portion between the first pattern and the second pattern, which is printed on the left end and the right end of the recording medium in the main scanning direction of the light beam. Since the amount is detected, it is possible to detect the amount of deviation considering both ends, and to correct the amount of deviation from the data of the amount of deviation, it is possible to obtain an optimal amount of correction.

According to a second aspect of the present invention, a group is formed by the pair of sets formed by the first pattern and the second pattern printed on the left end and the right end of the recording medium in the conveying direction, and all the vertical stripes are formed. It is also an effective means of the first invention that the first group constituted by (1) and the second group constituted by all horizontal stripes are printed on a recording medium.

By printing the first group, which is composed entirely of vertical stripes in the transport direction of the recording medium, it is easy to detect the gosa in the left-right direction and the magnification with respect to the recording medium. By printing the group, it is easy to detect the front-back direction and the slanting gosa with respect to the recording medium.

Preferably, the first pattern and the second pattern are printed and displayed so as to be visible, and as described in claim 4, the first pattern and the second pattern are preferably printed and displayed. It is further desirable to form the two patterns in different colors.

The first pattern and the second pattern are printed and displayed so as to be visually perceived, so that the amount of deviation can be easily visually recognized without using special detecting means. By forming the patterns in different colors, the amount of deviation can be more easily visually recognized.

According to a second aspect of the present invention, there is provided the image forming apparatus having a device for correcting a positional deviation of an image transferred to a recording medium, the positional deviation being caused by a transfer condition of a test pattern printed on the recording medium. In the method of correcting a transfer image position shift of the image forming apparatus, the test pattern is formed in a striped shape with a constant line width and a constant interval.
A pattern and a second pattern having an interval different from the first pattern are formed in a pair of pairs facing each other, and the pair of pairs is printed on the left end and the right end of the recording medium in the transport direction,
A shift amount is calculated from a value of a matching portion between the first pattern and the second pattern, and a shift amount of the left end or the right end, or a shift amount of the left end and the right end, or the left end and the right end An adjustment amount corresponding to the difference between the deviation amounts of the sections is provided to the correction device.

Here, the "shift amount of the left end portion and the right end portion" refers to the shift amount of the left end portion as described above.
It means the combination of the shift amount at the right end. Therefore, an adjustment amount corresponding to a shift amount of the left end or the right end, a combination of the shift amount of the left end and the right end, or an adjustment amount corresponding to a difference between the shift amounts of the left end and the right end is prepared in advance. Alternatively, the adjustment amount is calculated from each of the deviation amounts or the combination conditions, and the adjustment amount is provided to the correction device.

As described above, according to the present invention, the shift amount is determined from the value of the coincidence portion between the first pattern and the second pattern printed on the left end and the right end of the recording medium in the main scanning direction of the light beam. Since the calculation is performed, it is possible to obtain an adjustment amount for correcting the trajectory of the light beam at an optimum position in consideration of both ends, and the image shift can be corrected by a single adjustment operation using the adjustment amount. The operation is simplified and the manufacturing cost can be reduced.

[0023]

Embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention, but are merely illustrative examples. It's just

An embodiment of the present invention will be described with reference to the drawings. Before describing a method of detecting an optical gosa on a photosensitive drum by a light beam, an optical gosa correction device will be described. FIG. 2 is a configuration perspective view showing an embodiment of the image forming apparatus used in the present invention. In FIG. 2, an intermediate transfer body 21 is rotatably disposed in the image forming apparatus 1,
The photosensitive drums 20A and 20A
OB are arranged so as to be able to contact and roll at predetermined intervals.

An optical system for transmitting a light beam for forming an image on the outer peripheral surface of the photosensitive drum is disposed above the photosensitive drums 20A and 20B. The devices for developing the latent image on the photosensitive drum are omitted since they are not essential parts of the embodiment according to the present invention.

A polygon mirror 17 is arranged in the optical system, and light beams 19A, 1B from light sources 8A, 8B arranged in symmetrical positions on the outer peripheral surface of the polygon mirror 17.
9B is configured to enter through the condenser lenses 16A and 16B. Condensing lenses 18 corresponding to the light sources 8A and 8B facing the outer peripheral surface of the polygon mirror 17
A and 18B are arranged.

On the downstream side of the condenser lenses 18A, 18B, a reflector (mirror) 3 for reflecting the light beams from the condenser lenses 18A, 18B onto the photosensitive drums 20A, 20B is provided. The mirror assembly 14 is
b is attached to a frame (not shown) by an attachment 15. The mirror assembly 14 holds the mirror 3 between both ends 14a and 14b so as to be rotatable in order to change the reflection angle.

An end 14a of the mirror assembly 14 is arranged to be swingable by a position adjuster 9 described later.
In FIG. 4B, a shaft end 23 formed in a hemispherical shape is held rotatably (FIG. 4) in the recess 15a of the fixture 15.

FIG. 3 is a block diagram showing the position adjusting means. The position adjusting unit 23 includes a mechanism unit including the position adjuster 9 and an electric control unit. The position adjuster 9 includes a step motor 10, a pinion 11 provided on a rotation drive shaft of the motor 10, and a cam 13 formed integrally with a gear 12 rotated by the pinion 11. 13, the end 14a of the mirror assembly 14 is configured to be swingable in the horizontal direction in the figure as shown by the mirrors 3 and 3 '.

A mirror 3 is attached to the end 14a.
Step motor 22 is rotatable left and right around a
Is arranged. The electric control unit includes a control circuit 30, an interface 31, an input / output device 33, and a CPU 32. The control circuit 30 and the input / output device 33 are connected to the CPU 32 via the interface 31. The input / output device 33 is arranged on the operation surface of the image forming apparatus main body. The motor 22 and the motor 10 are configured to be controlled by the control circuit 30.

Next, the operation of the present embodiment configured as described above will be described. In FIG. 4, a reflector (mirror) 3
Shaft end 23 provided at the lower end 14b in the longitudinal direction of
Is formed in a hemispherical shape, and the hemispherical surface is slidably disposed in the recess 15 a of the fixture 15. Since the upper end 14a is configured to be swingable in a direction intersecting with the scanning direction of the light beam, the swing of the end 14a causes the mirror to tilt about the lower shaft end 23 as a fulcrum.

By moving the mirror 3 to 3 ', 3 ", the trajectory of the light beam on the photosensitive drum 20A changes to L', L, L". The degree of change on the lower side without the position adjusting means is small.
Therefore, by operating the position adjusting means 9 (FIG. 3), the mirror 3 is tilted with the shaft end 23 as a fulcrum, and the tilted portion is corrected.

Further, the reflecting surface 3 of the mirror 3 on the upper back side in FIG.
The light beam incident on e at any point in the scan,
The light enters the reflection surface 3e from the optical deflector in the same exit direction. The angle of incidence changes due to the swing of the reflecting surface 3e, and the angle α0 between the incident beam m0 and the exit beam n0, the angle α1 between the incident beam m1 and the exit beam n1, and the angle between the incident beam m2 and the exit beam n2. If α2 is formed, α1 <
α0 <α2, and the trajectories L ′, L, L ″ are formed on the photosensitive drum 20 by shifting in the axial direction of the photosensitive drum 20A as in S1, S0, S2. Is operated, the gosa in the left-right direction with respect to the recording medium conveyance direction is corrected.

Since S1, S0, and S2 are shifted on the photosensitive drum 20A in the front-rear direction with respect to the recording medium conveyance direction, the front and rear gossers are corrected by operating the position adjusting means.

Further, a motor 22 is disposed in the mirror assembly 14 (FIG. 3), and the reflection angle adjusting means is configured so that the mirror 3 can be rotated by the rotation of the motor 22.
As shown in the figure, the photosensitive drum 2 is moved from the optical deflector of the mirror 3 located at the position having the reflection surface 3eb via the reflection point P1.
It is possible to adjust the light beam to reach the point P4 or P7 via the reflection point P2 without changing the optical path length reaching P of 0A. In this case, the light beam can be adjusted with respect to the transport direction of the recording paper. The longitudinal gosa is adjusted.

The reflection point P1 from the optical deflector of the mirror 3
It is also possible to correct by changing the optical path length reaching P of the photosensitive drum 20A via the optical path. In this case, the magnification and the longitudinal gosa are adjusted in a complex manner.

In the above-described embodiment, the position adjuster 9 capable of adjusting the position of the mirror 3 is disposed at the longitudinal end 14a of the mirror assembly 14 in which the mirror (reflector) 3 is built. However, the present invention is not limited to this, and the position adjuster 9 may be disposed on the end 14b side.

The position adjusting means oscillates the reflector by means of a moving means movable in a direction perpendicular to the scanning direction of the light beam, which has an appropriate angle in the main operation direction of the light beam. Needless to say, any direction may be used as long as the directions intersect.

As described in detail above, in the present embodiment, the position of the irradiation beam on the photosensitive drum that enters via the reflector can be adjusted by driving only the position adjuster. The optical misalignment can be corrected by a single operation, the mechanism configuration is simplified, the adjustment operation at the factory is simplified, and the cost is reduced.

The optical deviation is a deviation of one irradiation beam irradiated on one photosensitive drum from another irradiation beam irradiated on the other photosensitive drum.
Front-back direction, left-right direction, inclination,
Magnification etc. occur, but it is not always necessary to eliminate only one of them. Since the present embodiment is configured to be able to correct at least one or a plurality of combination deviations, the operation can be eliminated by simultaneously canceling not only one but also a combination of a plurality of optical gosa with a single operation. Be simplified.

Next, an optical shift detecting method will be described. FIG. 1 is a diagram illustrating an aspect of a recording sheet on which a test pattern is printed. In FIG. 1, the recording paper 24 has a set A formed by first and second patterns 25a and 25b on the left side and a first stripe on the right side formed by vertical stripes. A first set B composed of a pattern 26a and a second pattern 26b;
The flock is printed.

Further, with respect to the direction of conveyance of the recording paper, a set C composed of the first pattern 27a and the second pattern 27b, all of which are composed of horizontal stripes, and a first pattern 28a, which is composed of all the horizontal stripes, of the right side. A second group composed of a set D formed by two patterns 28b is printed.

In the present embodiment, the upper scales of the vertical stripes constituting the sets A and B are at intervals of 20 dots, and the lower scales are at intervals of 19 dots. Further, the scales on the left side of the horizontal stripes constituting the sets C and D are at intervals of 20 dots, and the scales on the right side are at intervals of 19 dots. FIG. 1B shows an example of printing a test pattern when there is no deviation. The upper “2” graduation line and the lower “0” graduation line are aligned on a straight line and coincide with each other.

On the other hand, when there is a deviation, the position where the upper and lower graduation lines coincide changes, and in FIG. 1 (c), the upper part coincides with "7" and the lower part coincides with "5", and in FIG. "6" and "5" below
Matches. When the i-th of the upper scale line and the j-th of the lower scale line match, the shift amount X is 20 = dots on the upper scale and 19 dots on the lower scale. -2) × 20−j × 19 (1), and in the case of (c), 5 dots between the top and bottom,
In the case of (d), it can be read that the position is shifted by -15 dots. The sign of the shift amount is positive (+) when the lower side is shifted to the right with respect to the upper side, and is negative (-) when shifted to the left.

In general, the upper pitch is k and the lower pitch is h
(K ≠ h), a pattern in which the upper “m” and the lower “n” match when there is no shift, and when the upper “i” matches the lower “j”, the shift amount X Is calculated as follows: X = (im) × k− (j−n) × h (2) From this equation (2), it is possible to determine the amount of deviation between sets B to D.

The equation (2) is stored in a ROM connected to the CPU 32 shown in FIG. 3, and the shift amount X is calculated by inputting the i-th and j-th numbers to the input / output device 33.

The displacement of the group A is represented by Xa, and the displacement of the group B is represented by Xa.
Assuming that the shift amount of the pair B and C is Xc and the shift amount of the pair D is Xd, four types of shift amounts of left and right, magnification, up and down, and inclination can be obtained by the following equations. Left / Right Displacement at Left End (Displacement of Writing Position) = Xa (3) Magnification Displacement (Displacement from Reference Length) = Xb−Xa (4) Vertical Displacement at Left End (Displacement of Writing Start Position) = Xc (5) Amount of deviation of inclination = Xd−Xc (6)

The values of these equations (3) to (6) are temporarily stored in the RAM after the calculation, and the amount of adjustment of the motor 10 or the motor 22 corresponding to these values differs depending on the design specifications of each member. Is calculated by a table or a calculation formula stored in advance, and the deviation is corrected by the adjustment value.

Next, the operation of this embodiment will be described with reference to the flowcharts of FIGS. I / O device 33 not shown
(Fig. 3) to set the image shift adjustment mode,
When the chart output operation is performed (S1), the recording paper 24 shown in FIG. 1A is printed.

The values of both the vertical stripes 25a and 25b of the set A of the test pattern printed on the recording paper 24 are read and input to the input / output device 33, and the left end of the set A is obtained from the above equation (2). The left / right shift amount is calculated (S2). Similarly,
From the values of the two sets of vertical stripes 26a and 26b that match, the right / left shift of the right end of set B is determined (S3).

Using these values, the above equation (4) and
The correction amount M1 for left / right and magnification is obtained from a predetermined arithmetic expression or table (S4), and is temporarily stored. Next, the values of both the horizontal stripes 27a and 27b of the C set of the test pattern that match each other are input to the input / output device 33, and the vertical displacement of the left end of the C set is calculated from the above equation (2) (S5). ). Similarly, the right / left shift of the right end side of the D group is determined from the values of both the horizontal stripes 28a and 28b of the D group that match (S6).

Using these values, the above equation (6) and
A vertical / tilt correction amount M2 is obtained from a predetermined arithmetic expression or table (S7), and is temporarily stored. Next, the correction amounts M1, M2 are each compared with a predetermined value, and a correction amount equal to or larger than the predetermined value is determined as a correction candidate. At this time, if both correction amounts are correction candidates, the larger of the two correction amounts is set as the final correction candidate.

If the correction amount is less than the predetermined value, the image shift adjustment mode is ended. If the correction amount is equal to or more than the predetermined value (S8), the mode is adjusted so as to correspond to the correction amount. Motor 10 or motor 22 (FIG. 3)
Is driven for correction (S9), and the process returns to step S1.

In the above-described embodiment, the amount of deviation of the magnification and the amount of deviation of the inclination are expressed by the expressions (4) and (6), respectively. Although the difference in the amount is obtained, the present invention is not limited to this, and an adjustment amount corresponding to a combination of the amount of deviation at the left end and the amount of deviation at the right end is prepared in advance, or the amount of deviation of each of them is determined. The adjustment amount may be directly calculated from the combination condition and the adjustment amount may be provided to the correction device.

As described in detail above, this embodiment detects and corrects the optical position shift of the transferred image according to the transfer condition of the test pattern printed on the recording medium. A first pattern formed in a striped shape with a fixed line width and a fixed interval and a second pattern having a different interval from the first pattern are formed as a pair of pairs facing each other, and the pair of pairs is recorded. Since printing is performed on the left end and right end of the medium in the transport direction and the shift amount is detected from the value of the matching portion between the first pattern and the second pattern, the shift amount considering both ends can be obtained.

Further, the adjustment amount for correcting the trajectory of the light beam to the optimum position can be obtained quickly and accurately from the deviation amount.
The correction amount can be corrected by a single adjustment operation using the adjustment amount, the correction operation can be simplified, the manufacturing cost can be reduced, and the user can also perform the color shift correction corresponding to the variation of each product. .

Further, the present embodiment is configured to read the coincidence of the first and second striped patterns that intersect with the direction of deviation, and that the first and second patterns have different colors. By forming in the above, the amount of deviation between colors can be more easily visually recognized.

[0058]

As described above, according to the first aspect of the present invention, the displacement of the image of the image forming apparatus is detected according to the degree of transfer of the test pattern printed on the recording medium. A first pattern formed in a striped shape with a constant line width and a constant interval and a second pattern having an interval different from the first pattern are formed in a pair of pairs facing each other. Since the shift amount is detected from the value of the coincidence portion between the first pattern and the second pattern, which is printed at the left end and the right end of the recording medium in the main scanning direction of the beam, the conveyance direction of the recording medium It is possible to detect a shift amount in consideration of both ends printed on the left end portion and the right end portion, and it is possible to obtain an optimum correction amount when correcting the shift amount from the data of the shift amount.

Further, as set forth in claim 2, the group is constituted by the pair of pairs formed by the first pattern and the second pattern printed on the left end and the right end in the conveying direction of the recording medium, all of which are vertical stripes. And the second group, which is composed entirely of horizontal stripes, are printed on a recording medium.
By printing the first group composed entirely of vertical stripes, it is easy to detect the gosa in the horizontal direction and the magnification on the recording medium, and by printing the second group composed entirely of horizontal stripes, It is easy to detect the front-back direction and the inclined gosa.

Further, as described in claim 3, the first pattern and the second pattern are printed and displayed so as to be visible, and as described in claim 4, the first pattern and the second pattern are displayed. Because it is formed with different colors,
The first pattern and the second pattern are easily visible, and the amount of deviation can be easily visually recognized without using any special detection means. In addition, the first pattern and the second pattern have different colors. By forming in the above, the amount of deviation between colors can be more easily visually recognized.

According to a fifth aspect of the present invention, a positional deviation of an image of an image forming apparatus is corrected by a transfer condition of a test pattern printed on a recording medium, and the test pattern has a fixed line width and a constant line width. A first pattern formed in a stripe pattern at a constant interval and a second pattern having an interval different from the first pattern are formed in a pair of pairs facing each other;
The pair is printed on the left end and the right end in the recording medium conveyance direction, and the adjustment amount for correcting the trajectory of the light beam to an optimum position in consideration of both ends can be obtained quickly and accurately. Thus, the correction can be performed by a single adjustment operation, the correction operation can be simplified, the manufacturing cost can be reduced, and the user can easily perform the color shift correction.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a recording sheet on which a test pattern used in the present invention is printed.

FIG. 2 is a configuration perspective view showing an embodiment of an image forming apparatus used in the present invention.

FIG. 3 is a configuration diagram of a position adjusting unit.

FIG. 4 is an explanatory diagram illustrating a light beam trajectory on a photosensitive drum adjusted by swinging of a reflector.

FIG. 5 is an explanatory diagram illustrating a light beam arrival position on a photosensitive drum adjusted by a reflection angle adjusting unit of a reflector.

FIG. 6 is an explanatory diagram illustrating optical deviation of a light beam.

FIG. 7 is a flowchart illustrating an operation.

[Explanation of symbols]

1 Image Forming Apparatus 24 Recording Paper (Recording Medium) 25, 26, 27, 28 Test Pattern 25a, 26a, 27a, 28a First Pattern 25b, 26b, 27b, 28b Second Pattern

Claims (5)

[Claims] 1. A transfer image displacement detecting method of an image forming apparatus for detecting a displacement of an image transferred to a recording medium according to a transfer condition of a test pattern printed on the recording medium, wherein the test pattern is fixed. A first pattern formed in a striped shape at a fixed interval with a line width, and a second pattern having a different interval from the first pattern are formed as a pair of pairs facing each other. A method for detecting a transfer image position shift of an image forming apparatus, wherein printing is performed on a left end portion and a right end portion in a transport direction, and a shift amount is detected from a value of a matching portion between the first pattern and the second pattern. 2. A group comprising the pair of pairs formed by the first pattern and the second pattern printed on the left end and the right end of the recording medium in the transport direction, wherein the first group includes all vertical stripes. 2. The method according to claim 1, wherein a second group of horizontal stripes is printed on a recording medium. 3. The method according to claim 1, wherein the first pattern and the second pattern are printed and displayed visually. 4. The method according to claim 1, wherein the first pattern and the second pattern are formed in different colors. 5. A transfer image displacement correcting method for an image forming apparatus, comprising: a device for correcting a position shift of an image transferred to a recording medium, wherein the position shift is corrected according to a transfer condition of a test pattern printed on the recording medium. The test pattern is formed of a pair of pairs of a first pattern formed in a striped shape with a fixed line width and a fixed interval, and a second pattern having a different interval from the first pattern. A pair of pairs is printed on the left end and the right end of the recording medium in the transport direction, and a shift amount is calculated from a value of a matching portion between the first pattern and the second pattern, and a shift amount of the left end portion or the right end portion, Alternatively, the shift amount of the left end portion and the right end portion, or an adjustment amount corresponding to the difference between the shift amount of the left end portion and the shift amount of the right end portion is provided to the correction device. Correction method.